A double-heterojunction optical thyristor is presented, that can be turned off in a few nanoseconds simply by using the anode to a negative voltage exceeding a certain threshold. Previously, nanosecond-range turn-off could only be achieved by carrier extraction via contacts to either or both of the center two thyristor layers. Our tum-off method uses a PnpN layer structure for which punch-through of the n-layer under reverse bias of the P-n diode can be reached before this diode breaks down. We thus achieve an improvement in tum-off time by about 3 orders of magnitude over traditional two-terminal thyristors.